By way of example, a long-distance transmission line of the abovementioned type is known from the article “Gasisolierter Rohrleiter (GIL) für Hochspannungsübertragungen” [Gas-insulated tubular conductor for high-voltage transmissions], Josef Kindersberger, IEEE Joint IAS/PELS/IES and PES German Chapter Meeting, Goldisthal, Oct. 14, 2005, the teachings of which are incorporated herein by reference. A long-distance transmission line such as this is used to transmit high voltage, in particular as a technical alternative to an overhead line. In this case, the inner conductor is at high voltage, while the casing tube is grounded. Holding insulators are provided at regular intervals along the longitudinal or transmission direction in the interior of the casing tube, which holding insulators support the inner conductor with respect to the casing tube and provide insulation for the voltage difference.
Although a long-distance transmission line such as this is more costly than an overhead line, it requires considerably less maintenance effort, however, since the inner conductor is not subject to any external dirt and weather influences. In particular, a tubular line such as this also complies with stringent safety requirements, since it is comparatively insensitive to fires or other environmental catatrophes. The long-distance transmission line according to the present publication is filled in the interior for insulation purposes with an inert gas, in particular an N2—SF6 gas mixture.
The described tubular line can be laid underground or overhead. The inner conductor, which is in the form of a tubular conductor, in the disclosed long-distance transmission line carries an AC voltage. Support insulators, disk supports and bulkhead supports are described in order to support the inner line. Bulkhead supports in particular have the purpose of restricting the emergence of inert gas in the event of damage, since they compartmentalize the internal area at regular intervals.
The provision of inert gas with an increased insulating capability makes it possible to design the described tubular line with smaller diameters. On the other hand, the line must be kept sealed overall, which leads to not inconsiderable complexity in particular at junction points between individual sections or parts of the long-distance transmission line.